An integrated-circuit element and passive components are mounted on a front face of a multilayer substrate. A capacitor constituting a crystal-oscillator circuit is disposed inside the multilayer substrate. A cavity is provided in a rear face of the multilayer substrate. A crystal oscillator constituting the crystal-oscillator circuit is accommodated in the cavity, and the cavity is sealed with a sealing cap made of a conductive material. The sealing cap is fixed to an electrode pad provided on a motherboard with solder therebetween.